For centuries, people have mopped floors and left them to dry. Although it is possible to wipe a floor dry with absorbent material or a squeegee, a large number of floors are left wet every day in households, businesses, and public buildings. This practice also continues despite the fact that mops and window cleaning implements that combine a squeegee and a sponge are known. Many of these implements have a blade and sponge on different sides of the implement's handle, requiring the user to flip them over when switching from sponge to squeegee. In another design a knife removes liquid and dirt from a window and causes it to fall down on a spongy layer, which absorbs it. A reciprocating wiper attachment has also been proposed for window cleaners, car washing attachments, and hand mops.